1. Field of the Invention
The present invention relates to a compound, and particularly a phenanthrene compound having a polycyclic structure and semiconductor characteristics including electron transfer, electroluminescence, and photoluminescence.
2. Description of the Related Art
Molecular material used in organic light-emitting diodes (OLED), organic electroluminescence (EL) devices, or photovoltaic devices contains a conjugated molecule structure having double bonds alternating with single bonds to form sp2 hybrid orbitals such that the structure tends to form a plane. The conductivity of the conjugated molecule is accomplished by the transfer of the unpaired electrons through the π-π* delocalized conjugated bonds formed by the Pz orbitals of the carbon atoms. For such conjugated molecules, there is an energy gap (Eg) between HOMO (the highest occupied molecular orbital) and LUMO (the lowest unoccupied molecular orbital), and this provides the molecular material with semiconductor properties. The emitted light color depends on the energy gap. Nevertheless, due to the plane structure, the molecules tend to stack on each other and crystallize during film forming for applications, resulting in the device failure.
U.S. Pat. No. 6,268,072 (Eastman Kodak, 2001) discloses an electroluminescent polymer composition comprising a copolymer of adamantine, phenylene, and phenylanthracene. WO 02/26856 (CDT, 2002) discloses a polymer having a cyclic structural monomeric unit comprising a 5-member ring between a pair of phenyl rings, in which the two phenyl rings distort each other in the range of 50 to 750 and have a blue shift effect. U.S. Pat. No. 5,763,636 (Hoechst, 1998) discloses an electroluminescent polymer having a spiro-PF new structure. EP 1074600 (Sumitomo, 2001) discloses a copolymer having cyclic molecular moieties. JP Kokai No. 2003-55276 (Sony, 2003) discloses a phenanthrene electroluminescent material and a method of producing the same, in which the disclosed blue-light-emitting electroluminescent phenanthrene molecule and co-compound thereof are small molecules, which, upon reacting with other molecules, result in various blue-light-emitting electroluminescent molecules.
The techniques mentioned above attempt to prevent molecules from stacking on each other by a soft alkane chain, a distortion of the pair of phenyl rings in the main chain, or a norbornane group on the phenanthrene molecule, but only limited effect is achieved.
Hence, there is still a need for conjugated molecular material avoiding stacking during film formation for application in OLED, EL, photovoltaic devices, and the like.